Both public and private communications switching networks are arranged as groups of interconnected switches. A local service provider maintains a network of interconnected switches to provide service to its customers. The switches are coupled by trunks and each switch serves a number of connected station devices, such as telephones, terminals, and computers. To establish communication between two stations, a calling party dials a number of the called party. The interconnected switches route the call to the called party in accordance with the dialed number.
When customers change service providers or move locations within their service provider area it is desirable to keep the same number. For example, businesses may incur substantial costs if their telephone number changes due to the large inventory of business cards, stationery, and advertising materials. Local number portability (LNP) allows customers to change service providers or move to a different location in the current service provider area without changing their telephone number.
One of the problems associated with several LNP approaches is the requirement of software changes in the switches of the communications switching network. Other approaches, such as permanent call forwarding, introduce the problem of reduced calling features available to the customers.